Position sensors are included in various systems, devices, and environments. Moreover, various types of position sensors have been developed for inclusion into these various systems, devices, and environments. One particular genre of position sensor that has been developed is the transformer position sensor. A transformer position sensor typically includes a primary or excitation coil, a secondary or output coil, and a movable magnetically permeable core. When the excitation coil is electrically excited with an excitation signal, the output coil is inductively coupled to the excitation coil and supplies an output signal that is based on the position of the movable core. One particularly popular type of transformer position sensor is the variable differential transformer position sensor, which includes linear variable differential transformers (LVDTs) and rotary variable differential transformers (RVDTs). A variable differential transformer position sensor also includes an excitation coil, an output coil, and a movable magnetically permeable core. However, with variable differential transformer position sensors the output coil is typically configured as a pair of differentially wound coils that are electrically coupled in series.
The transformer position sensors described above are generally reliable and robust, but do suffer certain drawbacks. For example, many transformer position sensors exhibit a phase shift between the excitation signal and the output signal, which can lead to non-linearity. Many transformer position sensors may also exhibit undesirably low power factors. Various solutions have been proposed too address these drawbacks. These solutions include increasing the length of the magnetically permeable core, increasing the number of turns of the excitation coil, and using relatively high permeable material. Unfortunately, these proposed solutions exhibit their own drawbacks. In particular, these solutions can increase the impedance of one or both of the excitation coil and output coil, and adversely impact power factor.
Hence, there is a need for a transformer-type position sensor that exhibits improved phase shift between the excitation signal and the output signal, as compared with presently known sensors, without adversely impacting power factor. The present invention addresses at least this need.